Roger Guenveur Smith’s career suggests a belief in the great-man theory of history. Most people were introduced to him as the stuttering young man holding a photo of Malcolm X and the Rev. Dr. Martin Luther King Jr. in “Do the Right Thing.” Later he provided expansive, wandering theatrical meditations in “A Huey P. Newton Story” and “Who Killed Bob Marley?” And in “Frederick Douglass Now,” his scattered monologue at the Irish Arts Center, he places Douglass, the great abolitionist, in the context of the sweep of black history.

Standing jauntily in front of an American flag, he begins with a rapid-fire riff, darting among epochs and through a variety of contemporary cadences that mix the sounds of poetry slam, hip-hop and the old-style preacher.

“I am a movie star/Gun at the ready,” he spits out before pivoting. “My image plastered on plantation walls/Next to the malt liquor ads.” Jarring juxtapositions (“I know how to do the Black Panther stomp/And the Charleston”) spill out of Mr. Smith’s motor mouth with little apparent direction.

At the heart of the play are Douglass’s words, spoken, sung and emoted with entertaining conviction. At his best Mr. Smith finds resonance in these sober passages, like Douglass’s argument for why running away from his master was moral, in which he gives credence to the position of the master before dispatching it with brutal logic.

But the vibrant persona of Mr. Smith comes through much more than the character of Douglass. Less a dramatic portrait or a thoughtful theatrical essay than a star turn with an excess of personality, the play even quotes “Do the Right Thing” (twice). When discussing the great men of history, why not put yourself into the mix?

Donal O’Kelly’s historical drama “The Cambria,” running in repertory with Mr. Smith’s piece, is more traditional hero worship of Douglass. After escaping from slavery and writing his autobiography, Douglass went to Europe to gain sympathy for the abolitionist cause. The trip included a formative six months in Ireland where he spoke with Daniel O’Connell, was celebrated for his bravery and was inspired, he wrote in a letter, by the “total absence of all manifestations of prejudice against me.”

Mr. O’Kelly’s drama, where the playwright and Sorcha Fox nimbly play over a dozen roles, mostly takes place on a ship heading to Europe. Douglass, traveling under an assumed name, squares off with a Southern plantation owner (played with a cartoon snarl by Mr. O’Kelly). An Irish captain, struggling between sympathy for Douglass and a commitment to maintain order, is stuck in the middle.

With nary a wasted word, this well-told yarn on the high seas creates a persuasive world, even if it doesn’t escape some melodramatic clichés. The Douglass we meet in Mr. Smith’s play is larger than life and dynamic, while in Mr. O’Kelly’s quietly dignified portrait, he seems like a stoic standing firm against the overwhelming odds of his time. It’s a more realistic view of the world where inching history forward appears to be a mighty struggle.